Conventional 55 gallon drums do not fit well within ISO type ocean shipping containers. Specifically, the internal dimensions of ISO containers are approximately 913/4 inches by 2321/4 inches. Since standard 55 gallon drums are 23 7/16 inches in diameter at their rolling hoops, the drums cannot quite fit four abreast or ten in a row within the ISO containers. Similarly, not quite ten aligned rows can be fitted into an IS0 container. Therefore, as can be seen by the loading configuration shown in FIG. 4, a maximum of 76 normal 55 gallon drums can be placed into an ISO container when loaded in unpalletized form (the drums are typically stacked two high). When loaded on pallets, only 72 drums will fit within a container. Since this is clearly a waste of valuable cargo space, there have been various attempts by drum makers around the world to economically manufacture 55 gallon steel drums having dimensions suitable for fitting snugly into ISO containers.
Attempts to merely proportionally narrow the drums and compensate by making the drums taller are unsuitable since the additional height requirements make the drums to tall for many other applications. In addition, narrow and taller drums do not adapt to standarized materials handling and conveying systems. Simply eliminating the expanded rolling hoops is also unacceptable since tubular drums do not have sufficient sidewall strength to sustain the abuse of normal use. Therefore, some manufacturers have attempted to strengthen the sidewalls using corrugations and/or inward beads. However, such designs to not provide sufficient rigidity and resistance to implosion of the drum body by internal vacuums resulting from hot-filling the drum and its subsequent cooling in a sealed condition. Further, rolling hoops are needed to facilitate handling of the drums with conventional drum grippers. Therefore, there is a need for a drum construction that maximizes volume for a given external diameter yet maintains rolling hoops to facilitate handling by drum grippers and to strengthen the drum sidewall through the rigidizing effects of the expanding action.